Compositions for radiolabeling diethylenetriaminepentaacetic acid (DTPA)-dextran

Abstract

The subject invention relates to the compositions for radiolabeling Diethylenetriaminepentaacetic Acid (DTPA)-dextran with Technetium-99m and for stabilizing the DTPA-dextran Cold Kit. The composition contains Stannous Chloride ions to reduce 99m Tc-pertechnetate, Ascorbic Acid to reduce stannic ions to stannous ions to maintain a reducing environment, α,α-Trehalose to add bulk and to stabilize the lyophilized composition without interfering with the radiochemical yield, and Glycine to transchelate Technetium-99m under highly acidic conditions to facilitate radiolabeling DTPA-dextran with high radiochemical purity. In addition, the invention pertains to methods for making and using the compositions. The reconstitution of the lyophilized composition by 99m Tc-pertechnetate, resulting in radiolabeled 99m Tc-DTPA-dextran in a composition between pH 3 to 4. This invention contains a Diluent vial, which when used will shift the pH to a moderately acidic pH, which would provide less pain on injection and ease-of-use to clinical practitioners for adjusting its potency.

What is claimed is: 
     
       1. A method for stabilizing a DTPA-dextran cold kit for long-term storage, compromising the steps of:
 (a) adding an aqueous composition, compromising:
 (i) a sugar selected from the group of non-reducing disaccharides with a concentration up to 2% (w/v); 
 (ii) a pH buffer selected from a group of pH buffers in concentration range of up to about 0.5 mg/mL; 
 
 to a vessel containing about 90% of its target volume of degassed and deaerated water for injection; 
 (b) adding a non-sulfhydryl anti-oxidant wherein the concentration is in the range of about 0.5 mg/mL; 
 (c) adjusting the solution pH to a target pH of 3.2±0.2 with 6 N hydrochloric acid, while maintaining an inert gas sparge; 
 (d) adding a stannous salt wherein the concentration of the dihydrate form of the stannous salt is up to 75 micrograms/mL; 
 (e) adding a DTPA-dextran with a concentration of up to 0.50 mg/mL; 
 (f) adjusting the solution pH to a target pH of 3.2±0.2 with 6 N hydrochloric acid, while maintaining an inert gas sparge; 
 (g) adjusting the volume of the formulation to 100% of its target volume with degassed and deaerated water for injection; 
 (h) filtering the aqueous composition through a 0.22 micron filter and filling the aqueous composition in to glass vials with 1.0 mL±10%; 
 (i) removing the majority of the water content of the product, decreasing the residual moisture to about less than 1% water content by lyophilization; 
 (j) backfilling the lyophilized product with an inert gas to about 11.5 p.s.i. prior to stoppering the vials; 
 (k) crimping the lyophilized product vials with aluminum seals; and 
 (l) storing the crimped-sealed lyophilized product vials at either 2° to 8° C. or 25°. 
 
     
     
       2. The method of  claim 1 , wherein the non-reducing disaccharide is α,α-Trehalose Dihydrate. 
     
     
       3. The method of  claim 1 , wherein the pH buffer is Glycine. 
     
     
       4. The method of  claim 1 , wherein the non-sulfhydryl anti-oxidant is L(+)-Ascorbic Acid Sodium salt. 
     
     
       5. The method of  claim 1 , wherein the stannous salt is Stannous Chloride Dihydrate. 
     
     
       6. The method of  claim 1 , wherein the DTPA-dextran contains multiple DTPA groups conjugated to dextran in the molar ratio range of about 2:1 to 12:1. 
     
     
       7. The method of  claim 1 , wherein the DTPA-dextran contains dextran in the average molecular weight range of about 5,000 to 20,000 Daltons. 
     
     
       8. The method of  claim 1 , wherein the DTPA-mannosyl-dextran containing a molar ratio range of about 2:1 to 12:1 conjugated mannose groups to DTPA-dextran.